In some pharmacy order-picking systems, a large number of different drug packages of various sizes (piece goods) may be stored on elongated shelves in a chaotic fashion that is optimized as to space. Some pharmacy-order picking systems place drug packages on the shelves and/or retrieve them from the shelves with the help of an operating unit, wherein the operating unit has a gripping device for gripping the drug packages. For placing the drug packages on a shelf, the drug packages are identified, measured (e.g., the measurements are determined in three dimensions) and conveyed into a gripping area of the gripping device of a shelf operating system (see DE 195 09 951 C2, for example).